Democratic Party insiders say efforts to draft Sen. Bernard Sanders to launch a political party are foolish, doomed to fail and could do more to hurt than help the progressive cause. The pressure on Mr. Sanders to strike out on his own is intensifying now that former Labor Secretary Tom Perez was elected chairman of the Democratic National Committee , overcoming a stiff challenge from Rep. Keith Ellison and progressive activists who say the party ‘s primary race last year was rigged against the Vermont independent.